Piston to valve clearance issue????

[erniet17]

Hey all. I ordered my custom cam last week. Here is what they are sending me:

112* LSA
.545/.555 lift
228/235 duration

I am going to install this cam on a 1993 stock block with Edelbrock 60229 heads (1.90/1.60)

Does anyone have any idea if I will run into piston to valve clearance issues. I asked the tech over and over again but he said that it shouldn't be a problem. I just want to try and get other opinions.
Thanks

 

[90blacknight]

You should always measure PTV clearance, otherwise it's mostly a guessing game.

 

[347HO]

I'm just wondering how "custom" can it be?

You would have been asked to provide what pistons, what heads, what valves, springs, rockers, compression, deck clearance, transmission, chassis weight etc., and the camshaft designer would factor all that in.

Not to mention what 90blacknight already suggested... which is absolutely correct.

 

[5spd GT]

That that large of a duration, I could see some issues with stock pistons.

Do you have the intake centerline? 107? 108?

 

[erniet17]

The only info is what I posted. I told the tech that it was a stock bottom. He just asked me basic questions like what year car, motor, rockers, heads, tranny, gears and bolt-ons. I guess I am going to clay the piston just in case. I have never done it but I am assuming there's not much to it.

 

[erniet17]

Oh and I also called Comp and they recommended the XE274HR which is similar to the one I ordered.

 

[347HO]

That that large of a duration, I could see some issues with stock pistons.

Do you have the intake centerline? 107? 108?

What duration is too much and creates interference? What is the lobe proflle under the nose? Does that not matter... or does just duration? What about index of the camshaft in relation to crank?

If the cylinder heads are installed, you do not need to clay!
Do the necessary steps to remove both valve springs and install checking springs. Then put the piston at TDC and measure the clearance using a depth mic which is measured on the retainer. However much you can depress the valve... that's your clearance.
The neat thing about this method... you can check PTV throughout the camshaft events.

 

[5spd GT]

What duration is too much and creates interference? What is the lobe proflle under the nose? Does that not matter... or does just duration? What about index of the camshaft in relation to crank?

No.

Those are all good questions. I asked a couple questions to get at the valve events @ .050".

I said he COULD see issues. I did not say he will, and I did not say he will not run into issues. I said he could...

A stock lift camshaft (.444") with an early intake opening, a late exhaust closing, and a steep ramp rate (steep lobe) would hit.

 

[lang williams]

i ran into ptv clearance probs with my crane 2020 with the stock 87 bottom end. they are 530 lift an gtp heads with 1.84 valves.

 

[347HO]

i ran into ptv clearance probs with my crane 2020 with the stock 87 bottom end. they are 530 lift an gtp heads with 1.84 valves.

PTV has very, very little to do with how much lift is on a camshaft lobe.

This is what 5spd was leading into... and I wanted to ensure you cannot judge PTV by a camshafts duration because anyone reading events @ .050" tells you absolutely nothing about lobe ramp.

 

[5spd GT]

If you have an intake opening at 5* BTDC, and an exhaust closing at 5* BTDC, and you compare it to an intake opening at 10* BTDC, and an exhaust closing at 2* BTDC, assuming same lobe lift, duration, etc, could one not see that a steeper ramp rate is being used with the later one?

The intake is opening up at a sooner degree and the exhaust is closing closer to TDC all by using numbers at .050" for the valve events.

Using a Trickflow Stage 1 lobe lift as an example, you can see that lift is nothing to worry about with piston to valve clearance.

At peak lift, a 107.5 ICL (TFS-1 camshaft) is 2.156" down the bore, when the valve is open .499".

Lobe Lift - 1.6 RR - 1.7 RR - 1.8 RR

0.010 - 0.016- 0.017 - 0.018
0.020 - 0.032- 0.034 - 0.036
0.030 - 0.048- 0.051 - 0.054
0.040 - 0.064- 0.068 - 0.072
0.050 - 0.080- 0.085 - 0.090
0.060 - 0.096- 0.102 - 0.108
0.070 - 0.112- 0.119 - 0.126
0.080 - 0.128- 0.136 - 0.144
0.090 - 0.144- 0.153 - 0.162
0.100 - 0.160- 0.170 - 0.180
0.120 - 0.192- 0.204 - 0.216
0.130 - 0.208- 0.221 - 0.234
0.140 - 0.224- 0.238 - 0.252
0.150 - 0.240- 0.255 - 0.270
0.160 - 0.256- 0.272 - 0.288
0.170 - 0.272- 0.289 - 0.306
0.180 - 0.288- 0.306 - 0.324
0.190 - 0.304- 0.323 - 0.342
0.200 - 0.320- 0.340 - 0.360
0.210 - 0.336- 0.357 - 0.378
0.220 - 0.352- 0.374 - 0.396
0.230 - 0.368- 0.391 - 0.414
0.240 - 0.384- 0.408 - 0.432
0.250 - 0.400- 0.425 - 0.450
0.260 - 0.416- 0.442 - 0.468
0.270 - 0.432- 0.459 - 0.486
0.280 - 0.448- 0.476 - 0.504
0.290 - 0.464- 0.493 - 0.522
0.300 - 0.480- 0.510 - 0.540
0.310 - 0.496- 0.527 - 0.558
0.312 - 0.499- 0.530 - 0.562